In N-nitroso compound detection systems incorporating liquid chromatography and specific gas detection techniques, the liquid chromatorgraph produces an effluent in which various N-nitroso compounds are separated from each other and from other compounds in a sample in their time of exit from the chromatograph. If this temporal separation is impaired, the accuracy of measurement is adversely affected. Difficulty in efficient liquid-gas conversion may occur particularly with respect to non-volatile N-nitroso compounds which tend to vaporize unevenly or form deposits at the intended conversion point.
N-nitroso compounds are among the most carcinogenic compounds presently known. A single part per million dose may suffice to produce tumors. These compounds have been found in trace quantities in many materials which are contacted or taken internally by humans, such as artificial food additives, tobacco smoke and pesticides. In addition, they may be formed in vivo by taking internally the chemical precursors. In the continuing research into tumor producing substances, N-nitroso compounds require study and there is a need for tolerable levels of human consumption to be determined.
Considerable success has been achieved in the detection and measurement of N-nitroso compounds with systems such as that described in the U.S. patents cross referenced above. However, many such compounds are substantially non-volatile, are difficult to vaporize and are correspondingly difficult to measure with the same level of accurcy achieved with volatile compounds.
Accordingly, it is an object of the present invention to provide a liquid-gas interface capable of efficiently vaporizing non-volatile N-nitroso compounds to increase the accuracy achievable with N-nitroso compound detection systems.
It is a further object of the present invention to provide a liquid-gas interface between a liquid chromatograph and an N-nitroso compound detector which is capable of maintaining a timewise distribution of liquid chromatograph effluent.